Fastener driving tool



J. W. BAYER FASTENER DRIVING TOOL Jan. 28, 1969 Filed June 30, 1966 Sax (3b) Ma 4W.

4 T TORNEYS United States Patent ()1 zfice 3,424,361 FASTENER DRIVING TOOL Johann Wolfgang Bayer, Schaan, Liechtenstein, assignor to Hilti Aktiengesellschaft, Schaan, Liechtenstein Filed June 30, 1966, Ser. No. 561,939 Claims priority, application Germany, July 5, 1965,

A 49,653 US. Cl. 227- Int. Cl. B25c 1/14 3 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a fastener driving tool and guide for driving fasteners, such as studs, pins or nails, into materials such as wood, brick, stone, steel or the like.

In general the fastener tool is operated by an explosive cartridge and comprises a barrel serving as a guide for a driving plunger which, together with the fastener to be driven, is capable of free or unimpeded movement before the tip of the fastener strikes the receiving material. The fastener has a guide member thereon which cooperates with the barrel during movement of the fastener therethrough to hold the fastener in proper alignment. At the end of its driving stroke the piston is arrested by an abutment in the forward or muzzle end of the barrel.

When the plunger of such a driving tool is disposed at a fixed firing location in the barrel regardless of the length of the fastener being driven, the driving plunger may travel a short distance within the barrel in free flight before the fastener is actually driven into the receiving material. The extent or distance of this free flight is dependent, of course, upon the length of the pin being driven in relation to the effective length of the barrel. Such free flight permits an acceleration of the fastener before it engages the surface into which it is to be driven.

A safeguard essential to all such plunger type tools is that an abutment or stop be provided for the driving plunger to prevent it from leaving the barrel upon accidental operation of the tool when not directed towards an appropriate fastener-receiving surface, or in case the tool should be used for driving into a receiving material which is unexpectedly soft. One known way of producing such a safeguard is to provide the plunger with a shank or stem of reduced diameter to form an annular shoulder. A corresponding annular abutment face is provided by a counterbore in the muzzle of the barrel which is engaged by the annular shoulder on the plunger. A difliculty with this known construction is that the muzzle of the barrel must be long enough to accommodate long fasteners with the shank or stem portion of the plunger of a corresponding length. The tool must, therefore, have a substantial overall length and as the weight of the tool must be related to the Weight of the plunger in order to absorb recoil forces which are directly proportional to the plungers weight, the resulting too'l becomes excessively heavy.

To minimize these disadvantages it has been proposed to provide a barrel with a section of larger diameter between the muzzle and the rear end thereof so that the axial length of the muzzle portion of reduced diameter 3,424,361 Patented Jan. 28, 1969 can be kept small. With this construction, some guide means must be provided on the front end of the fastener to center it in the section of the barrel having a large diameter and such guide means must be capable of passing through the abutment of reduced diameter at the muzzle. One known solution to this problem is to provide a deformable plastics cap on the tip of the fastener which has an outside diameter corresponding to the large diameter part of the barrel. This cap is deformed, and perhaps partially destroyed, upon operation of the tool, by being forced through the reduced muzzle of the barrel.

However, after the tool has been operated a few times with such deformable plastic caps, the fragments of fractured caps accummulate in the barrel and produce a substantial risk to jamming 0f the plunger. Also, it is diflicult to insert fasteners into the tool because in some instances, depending upon the lengths of the fasteners, the caps have to be inserted manually into the muzzle of the barrel. Furthermore, the difference in diameter between the muzzle and normal bore of the barrel must be small so as to permit insertion of the plastic caps by deformation and without breakage. If the difference in diameter between the muzzle and normal bore is made to great, the plastic caps are apt to break upon entering the muzzle part, and debris therefrom will adhere to parts of the tool which are difficult to remove. Since the difference between the diameters of the muzzle and remainder of the barrel \must be small, the shoulder on the plunger must be correspondingly small and subject to excessive wear so that the tool will have a correspondingly short life.

One of the objects of the present invention is to provide an improved fastener driving tool which avoids the difliculties of prior constructions in inserting and driving fasteners while preventing the driving plunger from being accidently shot from the tool.

Another object is to provide a fastener driving tool having an abutment in the muzzle of its barrel of a shape to permit passage of a fastener and its guide while preventing the passage of the fastener driving plunger.

Still another object is to provide a fastener driving tool of the type indicated which is of simple and compact construction, economical to manufacture and one which is reliable in operation.

In order that the invention may be fully understood, it will be described further, by way of example, with reference to the accompanying drawings in which:

FIGURE 1 is a diagrammatic side elevational view of the barrel of a fastener driving tool in section which incorporates the novel features of the invention with the parts shown in an initial position prior to a driving operation;

FIGURE 2 is a view similar to FIGURE 1 but showing the forward end of the plunger engaging the abutment in the muzzle of the barrel at the end of a driving stroke;

FIGURE 3 is an end view of the tool as viewed in the direction of the arrow III in FIGURE 1 and showing the triangular shape of the fastener guide and opening in the abutment to adapt them to pass by each other;

FIGURE 4 is a view similar to FIGURE 3 but showing a modified guide and abutment configuration; and

FIGURE 5 is a View similar to FIGURE 1 but showing a tool of modified construction in which the driving plunger has a reduced shank for movement through th opening in the abutment.

In the drawings, FIGURES l to 3 are diagrammatic views of a fastener driving tool which serve to illustrate the novel features of the invention. The fastener-driving tool comprises a barrel 1 closed at its rear or breech end by a cartridge holder 2 having a chamber for a cartridge 20. Abutment elements or ribs 3a, 3b and 3c (hereinafter referred to generally by the reference numeral 3) are provided at the forward or muzzle end of the barrel 1.

The abutments 3a, 3b and 3c are engaged by the forward end of the plunger 4 at the end of a driving stroke as shown in FIGURE 2 to ensure that the plunger housed in the barrel 1 is held captive therein. The barrel 1 is intended to be loaded with a fastener 5, shown in the illustrated embodiment as a threaded pin or stud having a tapered shank, by inserting it through its muzzle. The rearward threaded end of the fastener is located in a recess 4a disposed axially in the driving plunger 4 and the forward end of the fastener is guided in the barrel 1 by a guide member 6 which is mounted on the shank adjacent its tapered tip with a tight friction fit.

In accordance with the present invention, the guide member 6 and the abutment 3 (formed by the elements 3a, 3b and 3c) are of such complementary shape and dimensions that the guide member 6 can pass through the abutment 3 without being impeded, deformed or destroyed. Thus, at the end of the fastener-driving operation, as shown in FIGURE 2, the guide member 6 is in a position where it has passed through the reduced opening in the muzzle of the barrel formed between the abutment elements 3a, 3b and 30 so that the muzzle can be moved away from the driven fastener without obstruction. This result is achieved, by forming the guide member 6 in a non-circular shape with peripheral reces:es to adapt it to pass through the opening in the muzzle of the barrel formed between the abutment elements or ribs 30, 3b, 3c in the muzzle of the barrel. As shown in FIG- URES l to 3, the guide member is in the form of an equilateral triangle with the corners rounded, and the abutment 3 is formed by the three complementary ribs 311, 3b and 3c projecting inwardly from the wall of the barrel 1 for engagement by the circular end of the plunger 4. It will be understood, however, that various other complementary shapes for the guide member and the abutment can be employed to achieve the result.

To operate the tool, a fastener 5 with a guide 6 mounted thereon is inserted into the barrel 1, rear end first, to engage the recess 4a in the plunger 4. During such insertion the triangular guide 6 is alined with the triangular opening in the abutment 3, as shown in FIGURE 3, and passed therethrough. The fastener 5 with the guide 6 thereon is then moved rearwardly in the barrel 1 to the position illustrated in FIGURE 1 and during such movement the corner edges of the guide engage and slide along the inside wall of the barrel to hold the forward tapered end of the fastener in substantial alinement with the axis of the barrel. The barrel 1 may be slightly recessed where it is engaged by the corners of the guide to hold the guide in alinement with the triangular opening in the abutment 3. During such loading the guide member 6 in addition to guiding the fastener, also acts as a friction element to initially hold a fastener in its proper position in the barrel. After the tool has been loaded, a cartridge 2a is inserted in the cartridge chamber 2.

The fastener 5 then may be driven by aiming the muzzle of the barrel against the surface of the receiving material and detonating the cartridge 20. The gases of the explosive charge expand in the barrel 1 and force the plunger 4 and fastener 5 forwardly through a driving stroke. As the fastener 5 moves forwardly, its forward end is held in substantial alinement with the axis of the barrel by the guide member 6. The triangular guide member 6, in turn, is held in alinement with and passes through the correspondingly shaped triangular shaped opening in the abutment 3. The end of the plunger 4, however, engages the abutment 3 to prevent it from being ejected from the barrel. Thus, the fastener 5 and guide 6 are ejected from the barrel without deformation while the plunger is retained in the barrel at the end of a fastener driving stroke.

A fastener driving tool having a modified form for the barrel muzzle and the guide means is shown in FIGURE 4. In this modification the abutment 3 is formed by a single rib or segment 3 protruding from the wall into the bore of the barrel 1, and the guide member 6' provided on the shank of the fastener 5 has an appropriate shape to pass through the muzzle without engaging the abutment. As shown, the guide member is of a generally rectangular shape with rounded edges.

FIGURE 5 illustrates still another embodiment of tool having an operation generally similar to the tool described above. In this embodiment, the driving plunger 4 is provided with a reduced diameter stem or shank part 4b directed towards the muzzle end of the barrel. The guide means on the shank of the fastener in the modified construction comprises a resilient guide member 6, such as has already been described with reference to FIGURES 1 to 3 and FIGURE 4 in combination with a high strength disc 7. The resilient guide member 6 serves to center the fastener 5 as it passes through the normal bore of the barrel 1 and is adapted to pass through the opening in the muzzle and disc 7 guides the fastener as it passes through the opening of reduced diameter in the muzzle. This modified construction is particularly satisfactory when the fastener 5 is being driven into a heterogenous material such as concrete. The outside diameter of the disc 7 which is preferably of steel, is such that the disc will clear the ribs 3a, 3b, 3c which form the abutment 3 as it passes through the muzzle of the barrel 1, and the radial inwardly projecting ribs are so shaped that the shank part 412 of the plunger 4 also can pass through the muzzle. To this end each of the ribs may be formed with a concave depression, as shown in FIGURE 3, and these depressions effectively provide bearing surfaces both for the disc 7 and the shank part 4b of the plunger 4. Thus, the curvatures at the inside edges of the abutment ledges 3a, 3b and 3c correspond to the outside diameter of the shank part 4b as well as the periphery of disc 7. Furthermore, the ribs 30, 3b and 3c define between them slots or channels 8, extending parallel to the barrels axis, through which the corners of the triangular flexible guide member 6 can pass and the depths of these slots correspond, of course, to the difference between the outside radii of the shank part 4b of the plunger 4 and the larger diameter part of the plunger. When the front or muzzle end of the barrel of FIGURE 5 is viewed in elevation it is similar to that of FIGURE 1 and consequently corresponds to FIGURE 3.

During a driving operation, the guide 6 guides the fastener 5 until it enters the abutment 3. The fastener 5 is then guided by both the member 6 and disc 7 through the muzzle by the radially-inward bearing surfaces of the ribs 3a, 3b and 36 until its end abuts the receiving material. Continued movement of the plunger 4 towards the abutment 3 then forces the fasteners shank through such disc 7 until a condition comparable with that of FIGURE 2 is achieved wherein the plunger 4 is arrested by the abutment 3.

I claim:

1. A fastener driving tool adapted to be used with a guide of generally circular configuration which surrounds the fastener in the barrel of the tool comprising a barrel having a breech end and an open muzzle end, a fastener driving plunger mounted for sliding movement in said barrel to drive a fastener, and an abutment in the muzzle end of said barrel engaged by the plunger at the end of its driving stroke to retain the plunger in the barrel, the guide and said abutment being shaped to permit the guide to pass through the open muzzle end of said barrel around the abutment while causing the end of the plunger to engage the abutment, the end of the plunger being circular to engage the abutment, and the abutment and guide having inner and outer peripheries, respectively, of a cooperating non-circular shape so as to pass by each other, the guide for the fastener and the opening at the inner periphery of the abutment being of cooperating triangular shape.

2. A fastener driving tool adapted to be used with a guide of generally circular configuration which surrounds the fastener in the barrel of the tool comprising a barrel having a breech end and an open muzzle end, a fastener driving plunger mounted for sliding movement in said barrel to drive a fastener, and an abutment in the muzzle end of said barrel engaged by the plunger at the end of its driving stroke to retain the plunger in the barrel, the guide and said abutment being shaped to permit the guide to pass through the open muzzle end of said barrel around the abutment While causing the end of the plunger to engage the abutment, the end of the plunger being circular to engage the abutment, and the abutment and guide having inner and outer peripheries, respectively, of a cooperating non-circular shape so as to pass by each other, the abutment being in the form of spaced segments projecting inwardly from the periphery of the barrel to form an opening therebetween.

3. A fastener driving tool adapted to be used with a fastener having a guide member of resilient material and a disc resistant to deformation mounted on the shank thereof comprising a barrel having a breech end and an open muzzle end, a fastener driving plunger mounted for sliding movement in said barrel to drive a fastener, and an abutment in the muzzle end of said barrel engaged by the plunger at the end of its driving stroke to retain the plunger in the barrel, the guide and said abutment being shaped to permit the guide to pass through the open muzzle end of said barrel around the abutment while causing the end of the plunger to engage the abutment, the end of the plunger being circular to engage the abutment, and the abutment and guide having inner and outer peripheries, respectively, of a cooperating non-circular shape so as to pass by each other, the abutment being in the form of peripherally spaced segmental ledges to form a non-circular opening therein, the inner edges of the segmental ledges being recessed to provide a circular opening at the center of smaller diameter than the plunger, the guide for the fastener adapted to pass through the opening between the ledges of the abutment, and the adapted to pass through the circular opening in the abutment.

References Cited UNITED STATES PATENTS 2,873,447 2/1959 Catlin ct a1 227-10 3,181,760 5/1965 Catlin et a1 22710 FOREIGN PATENTS 1,03 0,110 5/1958 Germany.

TRAVIS S. MCGEHEE, Primary Examiner. 

